In the art of making flexible polyurethane foam, it is known that by utilizing foam-forming formulations incorporating a highly reactive organic polyisocyanate and a high molecular weight polyol having a certain level of primary hydroxyl group content, a foam with improved resilience and other desirable physical properties can be accomplished. Such resulting foams have come to be referred to in the art as “high resilience” foams. Resilience is defined as the ability to return readily to original shape and dimensions after a deforming force has been applied and removed from a body. In polyurethane foam technology, the industry generally considers “Sag factor” to be the characteristic which differentiates high resilience foams from conventional foams. This Sag factor is a measure of support provided by a cushioning material and it represents the ratio of indent load deflection, ILD, at 65 percent deflection to that at 25 percent deflection (as per ASTM D-1564-64T). According to SPI standards, conventional, flexible foams exhibit a Sag factor of about 1.7 to 2.2, while high resilience foams display a factor of above about 2.2 to about 3.2.
High resilience foams have found widespread application as cushioning material in furniture and automotive seating. Most significantly, these foams have been utilized in the automotive industry for making molded auto seats. Most of the already established polyurethane foam techniques can be readily applied to high resilience foams. However, foam stabilization and collapsing, one particular area of technology, has been found to be markedly non-transferable. Due to the highly reactive nature of the reaction mixture from which the high resilience foams are prepared, such foams have been found to exhibit characteristic shrinkage upon demolding and cooling. Conventional foam reaction mixture components, which serve to stabilize the composition as it reacts, foams, and solidifies, are ineffective to prevent shrinkage in high resilience foaming reactions.
To meet the stabilization requirements of high resilience foams, there have been developed various approaches in which so-called “cell-openers” are incorporated in the foam. These added ingredients generally take the form of particles having diameters of about 2 micrometers or smaller. One technique involves the formation of “polymer-polyol” systems, which are produced from ethylenically unsaturated monomers and polyols, as exemplified by the disclosures in U.S. Pat. Nos. 3,383,351; 3,652,639 and 3,823,201. These polymer-polyols commonly are mixed with conventional polyether polyols and used as the starting polyol reactant.
Another U.S. Pat. No. 4,278,770, teaches that polyol compositions containing effectively dispersed particulate material featuring critical dispersion characteristics can be used to stabilize foam reaction in preparing high resilience polyurethane foam.
In U.S. Pat. No. 4,374,209, polymer particles are formed in a polyol by reacting an organic isocyanate with an olamine, an organic compound containing one or more hydroxyl groups and one or more amine groups. While this may provide a dispersion with utility in high resilience foam applications, the amine group is generally catalytic to the isocyanate-water reaction, resulting in a narrow processing lattitude. As such, the system is sensitive to small catalyst quantity variations. Very slight deviations from these limits can cause overly fast reaction with insufficient resilience occurring in the foam product.
When high resilience polyurethane foams are prepared it is important to ensure that the foam has a sufficient quantity of open cells to prevent shrinkage on cooling. The preparation of high resilience polyurethane foam is nearly always accompanied by the formation of some closed cells. The presence of closed cells substantially reduces the dimensional stability and flexibility of the foam while increasing its rigidity and brittleness. The closed cell content of a foam can be reduced by mechanical means such as crushing or flexing of the foam during its curing process causing the closed cells to be ruptured and opened. Alternatively, the extent of formation of closed cells can be minimized in part by careful selection of cell opening agents and their levels for the preparation of the foams.
A common problem with nearly all conventional cell openers is that they cause deterioration in the mechanical properties of the foams, especially compressive strengths. Since they do not contribute to the overall properties of the foam, except to open cells, it is desirable to reduce the quantity of cell opener required or modify it in such a way that it may contribute to the properties of the foam.
Accordingly, the present invention provides a cell-opening agent, which can assist in cell opening and maintain the mechanical properties of high resilience flexible polyurethane foam.